Multicolor flexographic machine for continuous printing on a tape, such as a plastic film or a paper web, having an automatic system for replacing the block-holding printing rollers.
As is known, two or more (up to eight) printing units are provided in multicolor flexographic machines currently in use. Each printing unit is arranged angularly spaced adjacent to an offset roller and is constituted by a block-holding roller, a screen roller and a drawing roller or by a doctor blade.
The operation of replacing the block-holding rollers is performed manually by two operators who come aside the machine with a hoist and disconnect and unload the rollers used in a previous printing operation on a suitable supporting trolley and replacing them with new block-holding rollers.
The entire operation is predominantly manual and thus it entails a rather long downtime during which the machine remains inactive, which negatively affects its productivity.
As a matter of fact this operation also comprises, besides removing of the printing units and replacement of the block-holding rollers, a series of manual preparatory setting up operations, such as release and locking of the retention means for the block-holding rollers, presetting of the replaced rollers to make sure that their angular position with respect to the offset roller is such as to obtain a correct overlay of the various colors on the printing material.
Handling and movement of the block-holding rollers at the various printing units of a flexographic machine are also made difficult owing to the narrow spaces available between one printing unit and the other.
Said operations must therefore be necessarily performed by highly qualified and trained personnel, which results in high operating costs.